This invention relates to resin-coated aggregates having a very low water absorbability, and further, if necessary, having a good stress-damping function.
Recently, artificial light weight aggregates (ALG) have been widely used as aggregates in light weight concretes owing to their light weight property. ALG is porous light weight aggregates prepared by firing shale, etc., as main raw materials.
On the other hand, ALG has a high water absorbability owing to its porous property and absorbs water during the mixing of concrete. Thus, it is necessary to prevent changes in the flowability of concrete. To this end, water content control must be thoroughly carried out before or during the mixing of concrete. Thus, the concrete mixing work becomes complicated or the resulting concrete is liable to undergo freezing damage.
To improve the water absorbability of ALG, it has bee already proposed to coat the surface of the aggregates with asphalt. However, there is still a problem that the asphalt-coated aggregates absorb water when subjected to a pressure of more than 10 atmospheres applied during the pumping of a light weight concrete containing the asphalt-coated aggregates, owing to the unsatisfactory strength, adhesion, etc. of the asphalt coating. That is, the asphalt-coated aggregates have an unsatisfactory effect on the water absorption prevention.
Furthermore, ALG has a poor resistance to an external stress owing to its porous property, and is liable to undergo rapid fatigue breakage due to repeated external stresses.
Not only ALG but also natural aggregates having a high water absorbability suffer form these problems.
An object of the present invention is to overcome these problems and to provide aggregates having a good effect on water absorption prevention, in which no water-absorbing phenomena take place even if exposed to a high pumping pressure.
Another object of the present invention is to provide aggregates having a function to absorb and damp any external stress in addition to its resistance to water absorption.
According to a first aspect of the present invention, the present aggregates comprise porous aggregates, at least whose surfaces are coated with a rigid phenol resin.
According to a second aspect of the present invention, there is provided a resin-coated aggregate comprising a porous aggregate body, an elastic layer made of a phenol resin elastomer deposited on the aggregate body, and a rigid phenol resin coated on the elastic covered body.